Lester, 29, won 19 of his 38 starts this year between the regular season and the postseason, combining for a 3.45 ERA (95 ER/248.0 IP) and 206 strikeouts. During the regular season, he went 15-8 with a 3.75 ERA and led the team in games started (33), innings pitched (213.1 IP), strikeouts (177), and quality starts (20). His 213.1 innings pitched set a single-season career high and ranked seventh in the AL, while his 33 starts matched a career mark for the third time and fell one shy of major league leaders.

The left-hander went 4-1 in the 2013 postseason en route to Boston's eighth World Series Championship, with a 1.56 ERA (6 ER/34.2 IP), a .205 opponent batting average, and 29 strikeouts in five starts. He won both of his World Series starts, allowing just one run and nine hits over 15.1 innings. His 0.59 ERA was the best by a Red Sox hurler making multiple starts in a World Series since Hugh Bedient in 1912 (0.50).

Originally selected by the Red Sox in the second round of the 2002 June draft, Lester owns a 100-56 record with a 3.76 ERA in 221 career regular season appearances (220 starts) in the big leagues beginning in 2006. Lester's 1,237 career strikeouts are the most ever by a Red Sox left-hander and rank fifth overall in franchise history. His lifetime .641 winning percentage ranks fourth among active pitchers with at least 125 decisions, while his 100 wins rank ninth among active lefties. He joins CC Sabathia as the only pitchers to record at least 15 wins in five of the last six seasons from 2008-13.